U.S. Bank is piloting voice biometrics for mobile login to credit card accounts. Bank employees participating in the pilot use a passphrase such as "my voice is my password" to access their account balances, search transactions and make a payment on their account in the mobile app.

"It is only employees with FlexPerks Travel Rewards Visa Signature cards who are involved in the U.S. Bank pilot," a U.S. Bank spokesperson said in an email.

The voice biometric system supplied by Nuance Communications replaces PINs, passwords and security questions with voice authentication. The technology can be used with call centers, IVR (interactive voice response) systems, mobile apps or the Web.

"Customers are becoming accustomed to using their voice to interact with their smartphones and can become frustrated with key-entering passwords," Dominic Venturo, chief innovation officer at U.S. Bank Payment Services, said in a statement. "Exploring a spoken passphrase login through this technology is a logical next step in our work in biometrics."

The pilot follows on from earlier work on the use of voice biometrics for customer authentication, which U.S. Bank and Nuance began in April 2013.

Wells Fargo is also testing voice recognition for mobile banking with its employees.

Neither bank has set a date for customer rollout of mobile apps for voice recognition login.

Read more about mobile banking.